1. Field of the Invention
The present invention relates to a broadcast communication system for communication through transmission and reception of data via a communication network among a plurality of user terminals, and particularly to a broadcast communication system for distributing received data to designated user terminals by accepting the data and designation of the data transmitting destination from any of the user terminals.
A communication group which is virtually formed on the network for making broadcast communication among a plurality of user terminals is called a “conference room”. This conference room may have various profiles and forms a communication group with the communication partners designated by the user terminals.
2. Description of the Related Art
In recent years, a transceiver technology utilizing a mobile communication network and a wireless LAN of cellular phones called PoC (Push-to-Talk over Cellular) and PoC/W (Push-to-Talk over Cellular/Wireless) has been put into the practical use. This transceiver function enables simultaneous voice communication to a plurality of partners on an IP communication network. A plurality of users, who can simultaneously communicate via voice are connected via a conference room on the network that is previously set or temporarily set. When a user, among those users connected in a same conference room, transmits a voice signal by acquiring the right to speak, the voice signals are distributed to the other users of the same conference room.
This transceiver function is primarily for communication by voice, but is capable of processing data for other than voice communication with improved cellular phones, for example. In addition, it is expected that communications will be further improved by distributing data for other than voice communication to the other users of the same conference room. However, the communication bandwidth for transmitting and receiving of the data is limited, particularly in the use of cellular phones. If voice and data communications other than voice are transmitted and received in combination, a delay and a fluctuation of the voice data are increased, resulting in a deterioration of a quality of the voice communication received. A method for avoiding such delay and fluctuation has been proposed to preset the communication bandwidth for voice communication and for the data other than the voice communication. However, in this method, if only one type of data is transmitted and received, since the communication network acquires respective data according to the preset fixed values, only the previously determined bandwidth is used. Thus, communication bandwidth reserved for data that is not transmitted is left unused, and thereby the available communication bandwidth is not used effectively. Thus, a problem exists that such conventional methods are inefficient in use of bandwidth.
A method has also been proposed in which information for varying a communication rate is collected from the user terminals taking part in the conference room whenever the right to speak is changed in the multiple-point conference system and the additional information such as picture information is distributed on the basis of the collected communication rate varying information. However, a problem still exists with such methods in that use of bandwidths is inefficient.